Paper splicing



plied across the sheet.

across the sheet.

Patented Aug. 17, 1954 PAPER SPLICING Dexter L. Wolfe and Earle A. Ruddy, Appleton, Wis., assignors, by mesne assignments, to The Institute of Paper Chemistry, Appleton, Wis., a corporation of Wisconsin No. Drawing. Application J une 19, 1950, Serial No. 169,068

8 Claims.

Thepresent invention relates, generally, to the splicing or interconnecting of lengths of'paper and, more particularly, to plastic composition in the form of a tape which isadapted to be employed in forminga splice or pastor for connecting lengths of paper.

Printing paper is made on the paper making machine in continuous strips which are collected in large rolls known as reels. The paper on the reels is then rewound into rolls of suitable size for the printing presses on which the paper is to be used. In forming the roll for the printing presses, any defective portions of the paper in the reel are cut out and the ends of the acceptable paper are spliced to produce s. continuous web in the roll which is to be used.

In making the usual type of splice during the rewinding operation, the paper ends to be spliced together are overlapped and a line of liquid adhesive such as dextrine in an aqueous dispersion or an adhesive in another liquid medium, is ap- The application of the liquid adhesive is usually effected by brushing or pouring the adhesive dispersion onthe sheet. The sheets are then pressed together andheated with an iron to set the adhesive after which the rewinding operation is resumed.

Splices made with a liquid adhesive are not entirely suitable for all papers and, in addition, interfere with printing operations. First, the liquid content of the adhesive causes the paper to wrinkle, thereby producing an uneven bond The uneven bond and the wrinkled sheet causes poor draw in the printing press, i. e. the paper does not pull through the press uniformly. This often causesbreaks in the web. In addition, as an uneven splice passes between the printing rolls in the press, the rolls are often moved out of register or synchronization. The loss of register is a particularly serious difiiculty since several pages of printed material may be made valueless before the printing rolls can be returned to register. Second, a splice made with liquid adhesive in the usual manner is non uniform in width and thicknessand gives an extremely poor appearance. Third, unless the operators exercise extreme .care when handling the liquid adhesive, it will spatter Onto the 011 and over the edges of the paper, r sul in in numerous breaks in the paper as it is unrolled. All of these disadvantages result in aconsiderable amount ofextra laborinthe printin operation and cause the waste of a large amount of paper. r

Despite the manydisadvantages ofusing a liquid adhesive, it has continued to be used because a splice resulting from such an adhesive is strong and it will withstand the high temperatures to which the paper is subjected when heat-set inks are used in the printing process. In some operations, high temperatures, e. g. 550 F. or greater, are produced in heat setting tunnels or by gas flames which are directed against the sheet to set the ink, these temperatures precluding the use of most of the other known adhesive materials. In addition to producing a strong though uneven splice, the use of liquid adhesives produces a spliced area which is readily broken up and dispersed in the beating operation when paper scrap or broke is reused.

Various attempts have been made to overcome the difficulties encountered when liquid adhesives aroused to make the splice. However, for various reasons all of these attempts have failed. For example, it has been proposed to employ a tape of thermoplastic material which will adhesively unite two lengths of paper, but in most instances these tapes have been so thick that they interfere with the register of the presses. If the tapes are made thinner, the adhesive strength is so reduced that the bond breaks under relatively minor strains. In addition, the known tapes which can be sealed to paper at temperatures below 350 F. (the temperature at which paper will scorch under an ordinarysealing operation) will produce a bond which is weakened by a momentary exposure to the high temperatures encountered in heat set printing. Additionally, none of the known plastic tapes will produce a spliced area which can be satisfactorily dispersed in the beater when paper scrap or broke containing the splice is being reclaimed.

Accordingly, the principal object of the inven-' tion is to provide an improved splice for both coated and uncoated papers which will maintain flexibility and strength in the printing press and which will overcome the deficiencies of the prior art splices and splicing methods. A more specific object of the invention is the provision of a tape of plastic composition which may be heat sealed to overlapping ends of lengths of paper to provide a flexible bond which will resist various forces and conditions encountered during the use of the paper. Other objects and advantages of the invention will become apparent from the following description.

We have discovered an improved plastic composition which can be fabricated into a thin tape, which can be disposed between two layers of paper and heated to provide a splice. The splic- 3 ing tape and the resulting splice exhibit all of the properties which are requisite in producing a splice which will satisfactorily connect lengths of paper for a printing operation. These properties are as follows? First, the tape fuses at a temperature below 350 F. Thus, a splice can be eifected without scorching the sheet during the splicing operation.

Second, the finished splice will withstand temperatures 550 F. or higher for the short interval at which they are encountered in heat-set print- Third, the finished splice is smooth and thin enough to pass through the printing rolls without causing an appreciable loss of register.

Fourth, the spliced area of paper connected by the tape disintegrates substantially completely in the beater.

Fifth, the tape from which the splice is made can be handled conveniently.

Sixth, the splice provides a flexible bond which is strong enough to withstand the forces which are encountered in the usual printing press and which is still thin enough to pass through the usual printing equipment without difficulty.

Seventh, the splice avoids puckering and wrinkling of the sheet with attendant avoidance of breaks in subsequent mill operations and in printing press operations.

In general, our improved splicing tape is fabricated from a film which is deposited by drying an aqueous emulsion or dispersion of polymerized vinyl acetate on a supporting surface, the aqueous emulsion including about 5 to- 20 per cent by weight (based upon the weight of the polymerized vinyl acetate) of a plasticizer. Various vinyl acetate plasticizers have been used successfully but particularly good results have been obtained with triethyleneglycol di 2 ethylbutyrate, dibutylphthalate, and monocresyl diphenyl phosphate. When triethyleneglycol di-Z-ethylbutyrate is used, the preferred percentage of plasticizer is 8 per cent based upon the weight of the polymer.

The finished tape is desirably of a thickness of about 3 mils or less, however, thicker tapes may be employed in certain operations but thicknesses of over 3 mils may interfere with printing operations. A tape 3 mils in thickness can be produced by casting the film in the desired thickness or by casting a thicker film and then stretching it after drying to reduce the thickness. Other methods of fabrication such as calendering may also be employed.

Preferably, the polyvinyl acetate in the emulsion should be polymerized to such a degree that the apparent molecular weight of the polymer is in the range of from about 100,000 to 150,000. However, higher or lower molecular weight compounds may be used with varying effectiveness. Under some conditions it is desirable to incorporate with the linear chain forming vinyl acetate monomer a minor percentage, e. g; l to 3 per cent by weight based upon the weight of the vinyl acetate monomer, of cross linking monomers such as the acrylic, methacrylic, and allyl esters. However, the addition of cross linking monomers is not necessary under most conditions.

After the film is cast and dried it may be cut into strips and rolled to produce a unit which is convenient to use in splicing paper. It is desirable to dispose a separator sheet between the superposed layers of tape to prevent the layers of tape from adhering to one another. This separator sheet may comprise a strip of paper which is impregnated with castor oil or any other suitable sheet having a surface to which the polymer will not adhere.

In use, the strip of tape made in accordance with the procedures set forth above is placed across the overlapped ends of two lengths of paper and is heated as by an iron or other suitable heating element to fuse the plastic tape to the surface of each of the lengths of paper. The splice produced by the fused plastic material has been found to have high strength, to be flexible in the printing presses, and to be readily dispersible in the beater when the scraps of paper are returned to the mill for further processing. Furthermore, the heat which is applied to the printed sheet in heat-set printing does not have any apparent effect upon the binding power of the splice. In addition, the splice lies flat and does not tend to pucker or wrinkle the sheet so that satisfactory register and draw in the press are obtained.

The following specific example of a method of making a splicing tape will illustrate one manner of carrying out the invention.

Example I An aqueous dispersion of polymerized vinyl acetate having a molecular'weight of approximately 125,000 was prepared, the dispersion containing 50' parts by weight of the polymer and 50 parts by weight of water. To this dispersion was added 4 parts by weight of triethyleneglycol di- Z-ethylenebutyrate and the mixture was vigorously stirred to produce a homogeneous dispersion. This dispersion, which contained 8 per cent by weight of plasticizer based upon the weight of the polymerized vinyl acetate, was then cast upon the glass plate and distributed to produce a film 3 mils thick. The film was then air dried at room temperature and after the moisture content had been reduced to about 5 per cent the film was cut into strips inch wide.

The strips made in accordance with the above procedure were then disposed between two overlapped pieces of coated paper. The paper had a basis weight of 50 pounds per standard ream (500 sheets 25 inches x 38 inches), the weight included 16 pounds of coating (total two sides). An iron, maintained at a temperature of 325 F. was run across the paper to effect a seal. Tests showed that the splice effected in this manner would not pull apart under stresses less than those required to break the sheet. The splice presented a smooth, unwrinkled appearance. The spliced area was subjected to a temperature of 550 F. until the paper was scorched and this temperature had no appreciable effect upon the splice. In addition, it was found that the spliced area disintegrated readily in a beater under standard operating conditions.

Samples of the spliced paper were run through a commercialheat-set printing press and it was found that there was no appreciable loss of register due to the spliced area passing through the printing rolls. In addition, the draw of the sheet remained flat and. even, occasioning no disturbance in the printing operation.

Example II An aqueous dispersion of polymerized vinyl acetate with methyl methacrylate added as a cross linking monomer before polymerization, was prepared, the vinyl acetate constituting 9'7 cent solids. To this dispersion was added .parts by weight-dibutylphtha'late as a plasticizer. The

dispersion was cast upon a polished metal surface in a film 3 mile thick. The film was then air .dried at room temperature to a moisture :content-m about 5 per lcent. llhe film was cut into strips 3/ inch wide, which were then removed from the supporting surface.

lllhestrips oi ifilmimadezinzaccordance with "the above method were then :disposed between two overlapped pieces of coated paper and tested in accordance with the :procedure set forthy in Examp'lel. lllhe ltest 'showed thatthe properties of the splice were substantiallyithe sameasthose obtained with the splicingmatenial of Example I.

A splice made in accordannewith theiinvention is flexible, the spliced together sheets do not exhibit wrinkling or puckering in the area of the splice, and the spliced area passes readily through printing presses without materially affecting the register of the printing rolls. The spliced area resulting when a splice is made in accordance with the invention is so smooth and even that the printing in the spliced area is acceptable and the printed sheet containing the splice may be used in all except the highest quality book and magazine work.

In casting the film, the solids content of the aqueous dispersion is not particularly critical, however, best results have been obtained when the solids content, the total of the vinyl acetate polymer and plasticizer, is in the neighborhood of 50 per cent. The aqueous dispersion may be air dried as in the specific example or the rate of drying may be increased by employing an infra-red or other drier which will not unduly raisethe temperature of the film.

As has been before pointed out, the film should be cast from an aqueous dispersion of the polymerized vinyl acetate and if a film is made from. a dispersion in organic liquid such as cyclohexanone or the like, the spliced area will not disintegrate satisfactorily in the beater. This will result in difficulty in manufacturing paper from broke containing spliced together paper scrap.

Various features of the invention which are believed to be new are set forth in the appended claims.

We claim:

1. A self supporting film of material which can be placed between two layers of paper and exposed to heat to thereby splice said pieces of paper together, said material fusing at a temperature below 350 F., being capable of withstanding short interval exposure to high temperatures, and being disintegrable in a paper making operation, said material consisting essentially of a mixture of a polymer of vinyl acetate containing a major proportion of polyvinyl acetate having an average molecular weight of from 100,000 to 150,000 and a plasticizer, the amount of plasti cizer being equal to from 5 to 20 per cent of the weight of said polymer of vinyl acetate, said material being produced by drying an aqueous dispersion of said mixture. i

2. A self supporting film of material which can be placed between two layers of paper and exposed to heat to thereby splice said pieces of paper together, said material fusing at a temperature below 350 F., being capable of withstanding short interval exposure to high temperatures, and being disintegrable in a paper making operation, said material consisting essentially of a mixture of a polymerof vinyl acetate containing a major proportion .of polyvinyl acetate having an average molecularweig ht of from 100,000

to 150,000 and dibutylph thalate, the amount of dibutylphthalate being equal to -f-rom25 :to 20 per cent of theweight of said polymer of vinyl acetate, said material being produced -by :d-rying an aqueous dispersion of said-mixture,

3. A self-*supporting film of material ior splicshort interval exposuremo high temperatures,

and being disintegrable in a paper making operation, said material consisting essentially 10f a mixture of a polymer of vinyl acetate containing a major proportion of polyvinyl -acetate having an average molecular weight-of from 100,000 to 150,000 and monocresyl diphenyl phosphate, the amount of monocresyl diphenyl phosphate being equal to from 5 to 20 per cent of the weight of said polymer, said material being produced by drying an aqueous dispersion of said mixture.

4. A self-supporting film of material for splicing paper, said material fusing at a temperature below 350 F., being capable of withstanding short interval exposure to high temperatures, and being disintegrable in a paper making operation, said material consisting essentially of a mixture of a polymer of vinyl acetate containing a major proportion of polyvinyl acetate having an average molecular weight of from 100,000 to 150,000 and triethylenglycol di-Z-ethylbutyrate, the amount of triethyleneglycol di-2-ethylbutyrate being equal to from 5 to 20 per cent of the weight of said polymer, said material being produced by drying an aqueous dispersion of i said mixture.

5. A self-supporting film of material for splicing paper, said material fusing at a temperature below 350 F., being capable of withstanding short interval exposure to high temperatures, and being disintegrable in a paper making operation, said material consisting essentially of a mixture of a polymer of vinyl acetate containing a major proportion of polyvinyl acetate having an average molecular weight of from 100,000 to 150,000 and triethyleneglycol di2-ethylbutyrate, the amount of triethyleneglycol di-2-ethylbutyrate being equal to about 8 per cent of the weight of said polymer, said material being produced by drying an aqueous dispersion. of said mixture.

6. A method for splicing paper sheets which comprises forming an aqueous dispersion consisting essentially of a vinyl acetate polymer containing a major proportion of polyvinyl acetate, from 5 to 20 per cent by weight of a plasticizer, based on the weight of polymer, and water, casting said dispersion onto a smooth supporting surface to form a film of polymer on said surface, drying said film on said surface, removing said film from said surface, applying said film between the overlapped ends of two pieces of paper, and then heating to a temperature below 350 F. to form a strong splice between said pieces of paper.

7. A method for splicing paper sheets which comprises forming an aqueous dispersion consisting essentially of a vinyl acetate polymer containing a major proportion of polyvinyl acetate having an average molecular weight of from 100,000 to 150,000, from 5 to 20 per cent by weight of a plasticizer, based on the weight of polymer, and water, casting said dispersion onto a smooth supporting surface to form a film of polymer on said surface, drying said film on said surface, re-

moving said film from said surface, applying said film between the overlapped ends of two pieces of paper, and then heating to a temperature below 350 F. to form a strong splice between said pieces of paper.

8. A method for splicing paper sheets which comprises forming an aqueous dispersion consisting essentially of a vinyl acetate polymer containing a major proportion of polyvinyl acetate, from 5 to 20 per cent by weight of dibutyl phthalate, based onthe weight of polymer, and water, casting said dispersion onto a smooth supporting surface to form a film of polymer on said surface, drying said film on said surface, removing said film from said surface, applying said film between the overlapped ends of two pieces of paper, and then heating to a temperature below 350 F. to form a strong splice between said pieces of paper.

ReferencesCited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Vinyl Products Bulletin V31147, published by the Du Pont Co. pages 1-6 (received Jan. 29, 1948).

Vinylite Polyvinyl Acetate Resins, published 1942 by Carbide and Carbon Chemicals Corn, pages 10, 11, 15, 16 and 1'7.

Polyvinyl Acetate, Du Pont, R & H Chemicals Dept. (1941), 4 pages. 

7. A METHOD FOR SPLICING PAPER SHEETS WHICH COMPRISES FORMING AN AQUEOUS DISPERSION CONSISTING ESSENTIALLY OF A VINYL ACETATE POLYMER CONTAINING A MAJOR PROPORTION OF POLYVINYL ACETATE HAVING AN AVERAGE MOLECULAR WEIGHT OF FROM 100,000 TO 150,000, FROM 5 TO 20 PER CENT BY WEIGHT OF A PLASTICIZER, BASED ON THE WEIGHT OF POLYMER, AND WATER, CASTING SAID DISPERSION ONTO A SMOOTH SUPPORTING SURFACE TO FORM A FILM OF POLYMER ON SAID SURFACE, DRYING SAID FILM ON SAID SURFACE, REMOVING SAID FILM FROM SAID SURFACE, APPLYING SAID FILM BETWEEN THE OVERLAPPED ENDS OF TWO PIECES OF PAPER, AND THEN HEATING TO A TEMPERATURE BELOW 350* F. TO FORM A STRONG SPLICE BETWEEN SAID PIECES OF PAPER. 